It is known that in lighting ignition circuits for igniting a gas discharge lamp, such as an automotive high intensity discharge (HID) headlamp, the ignition voltage may be obtained by pulse-forming networks, such as single stage resonant circuits. A resonant output pulse can be directly (or through transformer coupling) applied to supply igniting energy to the lamp.
A variable voltage output from an inverter circuit is commonly used to drive the resonant circuit. A required high voltage can be obtained by the resonant circuit when the switching frequency of the inverter matches the resonant frequency of the resonant circuit. One known disadvantage of this type of ignition circuit is that a relatively large resonant current is formed in the single resonant stage and this current can flux into the power switches of the inverter. This causes relatively large power losses and increases the cost and volume of the circuit in order to dissipate the resulting thermal load. Thus, it is desirable to provide an ignition circuit that in a cost-effective manner addresses the foregoing issues.